BIOLOGY APPLIED TO HEALTHFUL LIVING 555 



dirty human hands, and dust. Salads and other vegetables 

 not cooked should at least be carefully washed in water 

 which has been boiled. 



If there is reason to doubt the purity of drinking water, 

 heat it to the boiling temperature and pour into sterile 

 closed containers (such as earthen jugs). Longer boiling 

 is unnecessary and undesirable. These rules will protect 

 individuals. How to check the spread of intestinal diseases 

 and thus protect the public is a problem of sewerage, and of 

 insect control (see 330) . 



Intestinal diseases of children, especially in warm weather 

 ("summer complaint"), are largely due to stale milk. If 

 very clean, fresh milk is not available, then the milk 

 should be pasteurized ( 256). Thoroughly wash and sterilize 

 ( 256) daily all milk-bottles. 



It should be remembered that some bacteria of decay 

 may develop in foods and cause unhealthful conditions. 

 This and the fact that some disease germs will multiply 

 in milk and other foods should lead to caution. Foods 

 showing signs of decomposition should, of course, be rejected ; 

 but more important is the protection of foods from dust, 

 insects, and growth of bacteria. Remembering that bacteria 

 do not flourish when very cold, one thinks of the ice-box as 

 best for preventing growth ; but rarely is an ice-box cold 

 enough to preserve highly decomposable foods (such as 

 soup, gelatin, milk) for many days. Best of all methods 

 is heating to the boiling point daily the foods to be preserved 

 temporarily, and also keep them in an ice-box from day to 

 day. Thus disease germs, if present, will be killed ; and 

 ordinary decay, which might produce ptomaines (poisons in 

 foods) is prevented. 



486. Infection through Respiratory Organs. Tubercu- 

 losis is a good example. Tubercle bacilli may get into 

 the lungs (1) by close contact of healthy with tuberculous 

 persons (e.g., by kissing, and using common drinking cups or 



